A non-tyrosine kinase transmembrane protein, neuropilin-1 (NP-1) is a receptor for members of the VEGF family of angiogenic cytokines, particularly VEGF-A165, as wells as a receptor for a family of molecules called semaphorins or collapsins which play a key role in the guidance of neuronal axons during mammalian development. In particular, NP-1 is known to mediate the growth cone-collapsing and chemorepulsive activity of semaphorin 3A. NP-1 has been shown to play a role in the primary T-cell immune response.
There are a number of conditions in which NP-1 may have a significant role in pathology. Such conditions include stroke, ischaemic eye disease, cancer and rheumatoid arthritis.